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Learn how to create, name and drop a PRIMARY KEY constraint in MySQL, which uniquely identifies each record in a table. See examples of single and multiple column primary keys, and the syntax for CREATE TABLE and ALTER TABLE statements.
In MySQL, a primary key is a column or a set of columns that uniquely identifies each row in the table. A primary key column must contain unique values. If the primary key consists of multiple columns, the combination of values in these columns must be unique.
Learn how to create and use the primary key constraint in MySQL tables. The primary key is a column or a combination of columns that uniquely identifies each row in a table.
11 wrz 2012 · The following query gives the list of all the primary keys in the given database. SELECT DISTINCT TABLE_NAME ,column_name FROM INFORMATION_SCHEMA.key_column_usage WHERE TABLE_SCHEMA IN ('*your_db_name*');
MySQL supports an IGNORE keyword for INSERT, UPDATE, and so forth. If you use it, MySQL ignores primary-key or unique-key violations and continues processing with the next row.
1 cze 2024 · Learn the difference between primary key (PRI), unique key (UNI), and multiple key (MUL) in MySQL. See examples of how to use these keys to identify, constrain, and index records in a table.
2 maj 2022 · Learn what a primary key is, how to create and drop it in MySQL, and how to use auto-incrementing columns as default primary keys. See examples of creating tables with primary keys and altering them using SQL statements.
